The present invention relates to an improved fastening means for safety belts for cars and the like, of the type generally including an interlocking locking tongue and locking flap.
Previously known safety belt fastening means of this type generally include a locking tongue that is attached to the safety belt and is designed to engage with a locking device such as a locking flap. The locking flap, as well as other vital components of the locking means, such as expeller means and release means, are usually disposed in a locking case member, so that the entire fastening means is surrounded by a casing that is usually manufactured from a plastic material, in contrast to the remaining portions of the fastening means, which are manufactured from metal. The connection or engagement of the locking tongue and locking flap is generally released by a simple release mechanism, for example, a push-button. A serious drawback of conventional fastening means is the wear due to friction between the various metal components thereof. Vital parts, like the locking tongue, the locking flap, and the locking case are exposed to friction and consequently to wear as a result of repeated engagements of the locking tongue and locking flap.
Such wear will gradually result in an impairment of functional security. To comply with prevailing international requirements as to functional security of the fastening means, lubricants are today used to reduce the friction between components of the fastening means and, thus, the wear. Lubricants, however, have the disadvantage that they may rub off on the user. Also, lubricants bind dust and the like, so that the lubricant no longer has the expected effect but, on the contrary, contributes to increased friction.
Lately, regulations have been formulated regarding the maximum force permitted for releasing safety belt locking mechanisms. The critical values of said force are at present at maximum 6 kp and minimum 1 kp. In Applicant's Norwegian Patent NO-PS No. 138 431, published May 29, 1978, a fastening means is described that is essentially characterized by the fact that in the push-button release mechanism, the extension of the push-button comprises a cam surface which is directed away from a locking tongue and which provides a sloping curve that turns into an upright, nose-like portion, the lower end of which is provided with a notch or the like into which the locking flap slides with one end and is locked. Common to this fastening means and other conventional fastening means is that the force used to release the fastening means in a non-loaded state is close to the above-mentioned minimum force of 1 kp. The force used in the start phase of the opening procedure, however, often will be below this minimum value, and may easily result in unintentional opening of the fastening means on light contact with the push-button.
An object of the present invention is to provide a fastening means for safety belts for cars that does not have the above disadvantages.
Another object of the invention is to provide a light and inexpensive construction of a fastening means, that is also resistant to forces that tend to break the fastening means. Such forces would, as known, occur in connection with heavy loads exerted during car crashes and similar events.